Use of chiral, uncharged metal compounds as dopants for liquid-crystalline materials
The present invention relates to the use of chiral, uncharged compounds of the general formula Ia
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)nL]2Mexe2x80x83xe2x80x83(Ia) 
or Ib
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)nL]Me(Lxe2x80x2(xe2x80x94Y6xe2x80x94M2xe2x80x94Y5xe2x80x94A2xe2x80x94Y4xe2x80x94P2)nxe2x80x2)mxe2x80x83xe2x80x83(Ib), 
in which, independently of one another,
P1 and P2 are hydrogen, C1-C12-alkyl, a group which is polymerizable or suitable for polymerization, or a radical which carries a group which is polymerizable or suitable for polymerization,
Y1 to Y6 are a single chemical bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94N(R)xe2x80x94, xe2x80x94(R)Nxe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94N(R)xe2x80x94, xe2x80x94(R)Nxe2x80x94COxe2x80x94Oxe2x80x94 or xe2x80x94(R)Nxe2x80x94COxe2x80x94N(R)xe2x80x94,
R is hydrogen or C1-C4-alkyl,
A1 and A2 are spacers having from one to 30 carbon atoms,
M1 and M2 are mesogenic groups,
nxe2x80x2 and n are values of 0 or 1,
m is a value of 1, 2 or 3,
where the m Lxe2x80x2(xe2x80x94Y6xe2x80x94M2xe2x80x94Y5xe2x80x94A2xe2x80x94Y4xe2x80x94P2)nxe2x80x2 groups in the formula Ib may be different,
Me is a transition metal from the fourth, fifth or sixth period, with the exception of technetium, silver, cadmium, gold, mercury and the lanthanoids, or a main-group element from group 14 (in the IUPAC system), with the exception of carbon and lead,
L is a tridentate ligand of the formula II 
in which
U, V and W are nitrogen-, oxygen-, phosphorus- or sulfur-containing groups which contain a nitrogen, oxygen, phosphorus or sulfur atom respectively having at least one free electron pair via which the coordination to the center Me takes place,
b1 and b2 are alkylene or alkenylene bridges having two or three carbon atoms which are bonded to the nitrogen, oxygen, phosphorus or sulfur atom of the groups U and V (for b1) or of the groups V and W (for b2) and which, in the case of a C2-alkenylene bridge, may be substituted by up to two, in the other cases by up to four organic radicals having up to 12 carbon atoms, and in which two adjacent carbon atoms in the alkylene or alkenylene bridge may be part of an unsubstituted or substituted, simple or benzo-fused benzene ring, and
Lxe2x80x2 is an organic radical having up to 12 carbon atoms,
as dopants for liquid-crystalline materials.
The invention furthermore relates to compounds of the general formula IIIa
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)L]2Mexe2x80x83xe2x80x83(IIIa) 
and IIIb
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)L]Me(Lxe2x80x2(xe2x80x94Y6xe2x80x94M2xe2x80x94Y5xe2x80x94A2xe2x80x94Y4xe2x80x94P2)nxe2x80x2)mxe2x80x83xe2x80x83(IIIb), 
where the variables P1, P2, Y1 to Y6, A1, A2, M1, M2, nxe2x80x2, m, Me, L and Lxe2x80x2 are as already defined above.
Cholesteric liquid-crystal mixtures are usually prepared using a liquid-crystalline (nematic) base material and one or more optically active dopants. This enables the optical properties of the mixture to be varied by simply changing the ratio of liquid-crystalline base material to dopant.
Although chiral dopants for liquid-crystalline phases are known in large number from the scientific and patent literature, relatively little is known on the use of chiral, uncharged metal compounds as dopants for liquid-crystalline materials.
The phase behavior of chiral copper (II), nickel (II), oxovanadium (IV) and palladium (II) complexes of 4-(4-heptyloxybenzoyloxy)-N-(S)-2-methylbutylsalicylaldehyde, in which the central ion is tetracoordinated, has been investigated by W. Pyzuk and Yu. Galyametdinov in Liquid Crystals, 1993, Vol. 15, No. 2, pp. 265-268. The salicylaldehyde derivative here functions as bidentate ligand, via which the oxygen atom of the deprotonated hydroxyl group and the nitrogen atom of the Schiff""s base of the aldehyde group are coordinated.
J. Buey et al. in Chem. Commun., 1999, pp. 441-442, have described the phase behavior of a monocyclic and of a bicyclic chiral palladium (II) complex and of mixtures of these complexes with a nematic host material. The palladium atoms are in each case tetracoordinated; in the monocyclic complex, the coordination of the two different bidentate ligands takes place via a carbon atom and a nitrogen atom or via an oxygen atom and a nitrogen atom. In the bicyclic complex, the palladium centers are linked to one another via a sulfur bridge and a carboxyl bridge, with the other coordinations to the palladium centers in each case being formed via a carbon atom and a nitrogen atom of two identical ligands.
G. Piao et al. in Synthetic Metals, 101, 1999, pp. 92-93, have described the polymerization of acetylene in the presence of a catalyst comprising a chiral titanium compound and triethylaluminum. One of the titanium compounds investigated is a titanium complex in which the metal center is tetracoordinated to two axial-chiral, bidentate (R)- or (S)-6,6xe2x80x2-di(4-(trans-4-n-pentylcyclohexyl)phenoxy-1-hexyl)-2,2xe2x80x2-dihydroxy-1,1xe2x80x2-binaphthyl ligands via the oxygen atoms of the deprotonated hydroxyl groups. The (R)- or (S)-titanium tetrakis(2-octanolate) was investigated as a further titanium compound. In addition, the preparation of chiral nematic phases by mixing the titanium compounds with liquid-crystalline materials is also mentioned.
Investigations by A. F. Drake et al. On the helical twisting power of trisacetylacetonate (xe2x80x9cpentane-2,4-dionatoxe2x80x9d) complexes of trivalent cobalt, chromium, ruthenium, iridium and rhodium in liquid-crystalline materials are described in Chem. Phys. Letters, Vol. 110 (6), 1984, pp. 630-633. The central ions of the complex are hexacoordinated via the oxygen atoms of the three bidentate acetylacetonate ligands in each case. Only the type of coordination of the achiral ligands to the central atom provides the metal acetylacetonates described with chirality, which differentiates these compounds from those mentioned previously in which the ligands are themselves already chiral.
It is an object of the present invention to provide further chiral metal compounds which are suitable as dopants for liquid-crystalline materials.
We have found that this object is achieved by the compounds of the formulae IIIa and IIIb described at the outset and by the use of the compounds of the formulae Ia and Ib described at the outset.
The invention covers chiral metal compounds whose chirality is caused by chiral ligands L/Lxe2x80x2 and by the spatial arrangement of achiral ligands L/Lxe2x80x2 around the Me center.
The following comments regarding the meanings of the variables P1, Y1 to Y3, A1 and M1 in the compound Ia, the variants P1, P2, Y1 to Y6, A1, A2, M1 and M2 in the compound Ib and the variables P2, Y4 to Y6, A2 and M2 in the compound IIIb are of course only of relevance if the variables n or n and nxe2x80x2 or nxe2x80x2 respectively in the corresponding formulae adopt the value 1.
Possible spacers A1 or A1 and A2 in the compounds Ia, Ib, IIIa and IIIb are all groups known to the person skilled in the art for this purpose. In general, the spacers contain from one to 30, preferably from one to 12, particularly preferably from one to six, carbon atoms and consist predominantly of linear aliphatic groups. They may be interrupted in the chain, for example by non-adjacent oxygen or sulfur atoms or imino or alkylimino groups, for example methylimino groups. Possible substituents for the spacer chain are also fluorine, chlorine, bromine, cyano, methyl and ethyl.
Examples of representative spacers are the following: 
where u is from 1 to 30, preferably from 1 to 12, v is from 1 to 14, preferably from 1 to 5, and w is from 1 to 9, preferably from 1 to 3.
Preferred spacers are ethylene, propylene, n-butylene, n-pentylene and n-hexylene.
The mesogenic groups M1 or M1 and M2 used in the compounds Ia, Ib, IIIa and IIIb can be all groups which are suitable as such to the person skilled in the art.
Particularly suitable are mesogenic groups having the general structure IV
(xe2x80x94Txe2x80x94Y7)rxe2x80x94Txe2x80x94xe2x80x83xe2x80x83(IV) 
where the variables have the following meanings:
T is a divalent, saturated or unsaturated carbocyclic or heterocyclic radical,
Y7 is a chemical bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Coxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94, xe2x80x94COxe2x80x94N(R)xe2x80x94, xe2x80x94(R)Nxe2x80x94COxe2x80x94,xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94N(R)xe2x80x94, xe2x80x94(R)Nxe2x80x94COxe2x80x94Oxe2x80x94 or xe2x80x94(R)Nxe2x80x94COxe2x80x94N(R)xe2x80x94, and
r has a value of 0, 1, 2 or 3, where for r greater than 0, both the radicals T and the groups Y7 may be identical or to different from one another.
The radicals T may be ring systems which are substituted by fluorine, chlorine, bromine, cyano, hydroxyl, formyl, nitro, C1-C20-alkyl, C1-C20-alkoxy, C1-C20-alkoxycarbonyl, C1-C20-monoalkylaminocarbonyl, C1-C20-alkylcarbonyl, C1-C20-alkylcarbonyloxy or C1-C20-alkylcarbonylamino. Preferred radicals T are the following: 
Examples of suitable mesogenic groups M1 or M1 and M2 are the following: 
Further possible mesogenic groups M1 or M1 and M2 comply with the following formulae: 
The (unsubstituted) mesogenic groups indicated above may of course, corresponding to the abovementioned examples of possible radicals T, also be substituted by fluorine, chlorine, bromine, cyano, hydroxyl, formyl, nitro, C1-C20-alkyl, C1-C20-alkoxy, C1-C20-alkoxycarbonyl, C1-C20-monoalkylaminocarbonyl, C1-C20-alkylcarbonyl, C1-C20-alkylcarbonyloxy or C1-C20-alkylcarbonylamino. Preferred substituents are, in particular, short-chain aliphatic radicals, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, and alkoxy, alkoxycarbonyl, alkylcarbonyl, alkylcarbonyloxy, alkylcarbonylamino and monoalkylaminocarbonyl radicals which contain these alkyl groups.
C1-C12-alkyl radicals which may be mentioned for P1 or P1 and P2 in the compounds Ia, Ib, IIIa and IIIb are branched or unbranched C1-C12-alkyl chains, for example methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl-, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl and n-dodecyl.
Preferred alkyl radicals for P1 or P1 and P2 are the branched or unbranched C1-C6-alkyl chains, for example methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl-, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl and n-hexyl.
Suitable groups which are polymerizable or suitable for polymerization or suitable radicals which carry a group which is polymerizable or suitable for polymerization (such groups are also referred to below as xe2x80x9creactive radicalsxe2x80x9d) for P1 or P1 and P2 are the following: 
xe2x80x94Nxe2x95x90Cxe2x95x90O, xe2x80x94Nxe2x95x90Cxe2x95x90S, xe2x80x94Oxe2x80x94Cxe2x89xa1N, xe2x80x94COOH, xe2x80x94OH or NH2 
where the radicals R1 to R3 may be identical or different and are hydrogen or C1-C4-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl.
Of the polymerizable groups, the cyanates can trimerize spontaneously to give cyanurates. The other groups mentioned require further compounds containing complementary reactive groups for polymerization. Thus, for example, isocyanates can polymerize with urethanes and with amines to give urea derivatives. An analogous situation applies to thiiranes and aziridines. Carboxyl groups can condense to form polyesters and polyamides. The maleimido group is particularly suitable for free-radical copolymerization with olefinic compounds, for example styrene or compounds containing styrene structural units.
The complementary reactive radicals here, together with the reactive radicals corresponding to them, may be present in one and the same compound Ia, Ib, IIIa or IIIb (meaning that this compound can potentially also polymerize with itself) or in a further compound Ia, Ib, IIIa or IIIb. However, these complementary reactive radicals may also, together with the corresponding reactive radicals, be present in one and the same (auxiliary) compounds or in further (auxiliary) compounds of this type.
Polymerizable groups which should be particularly emphasized are the acrylate, methacrylate and vinyl radicals.
Me is a transition metal from the fourth, fifth or sixth period, with the exception of technetium, silver, cadmium, gold, mercury and the lanthanoids, or Me is a main-group element from group 14 (in the IUPAC system), with the exception of carbon and lead. In particular, Me is titanium, chromium, manganese, iron, cobalt, copper, zirconium, molybdenum, ruthenium, rhodium or tungsten, or silicon.
The tridentate ligand L conforms to the general formula II 
in which U, V and W are nitrogen-, oxygen-, phosphorus- or sulfur-containing groups which have a nitrogen, oxygen, phosphorous or sulfur atom respectively having at least one free electron pair via which the coordination to the central ion Me takes place.
The compounds of the formulae Ia, Ib, IIIa and IIIb preferably contain ligands L in which V in the formula II is a nitrogen-containing group.
The compounds of the formulae Ia, Ib, IIIa and IIIb particularly preferably contain ligands L in which V in the formula II is a nitrogen-containing group, and U and W are either both an oxygen- or phosphorus-containing group or one of the groups U and V is an oxygen-containing group and the other is a nitrogen-containing group, i.e. the formula II breaks down in this particularly preferred case into the following formulae: 
where R*N, OR*, SR* and P(R*)2 are generally nitrogen-, oxygen-, sulfur- or phosphorus-containing groups. It should be noted here that R* can also be a second bond within the bridge b1 or b2, which means that, for example, R*N may also correspond to an imino group xe2x80x94Nxe2x95x90.
According to the condition that the metal compounds Ia, Ib, IIIa and IIIb should be uncharged, the nitrogen-, oxygen-, sulfur- or phosphorus-containing groups must carry corresponding formal charges or it must be possible for the corresponding groups to be converted into those having the requisite formal charge, so that, where appropriate taking into account radicals Lxe2x80x2, neutralization of the charges at the central ion Me results.
b1 and b2 in the formula II correspond to alkylene or alkenylene bridges having two or three carbon atoms which are bonded to the nitrogen, oxygen, phosphorus or sulfur atom of the groups U and V (for b1) or of the groups V and W (for b2) and which, in the case of a C2-alkenylene bridge, may be substituted by up to two, in the other cases by up to four organic radicals having up to 12 carbon atoms, and in which two adjacent carbon atoms in the alkylene or alkenylene bridge may be part of an unsubstituted or substituted, simple or benzo-fused benzene ring.
Examples which may be mentioned of possible organic radicals having up to 12 carbon atoms of this type, but also of the meaning of Lxe2x80x2, are branched and unbranched alkyl radicals, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl and n-dodecyl, but also cycloalkyl radicals having branched or unbranched alkyl chains, for example cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 1-methylcyclopropyl, 1-ethylcyclopropyl, 1-propylcyclopropyl, 1-butylcyclopropyl, 1-pentylcyclopropyl, 1-methyl-1-butylcyclopropyl, 1,2-dimethylcyclopropyl, 1-methyl-2-ethylcyclopropyl, cyclooctyl, cyclononyl or cyclodecyl.
Furthermore, organic radicals having up to 12 carbon atoms of this type, but also the meaning of Lxe2x80x2, may also be taken to mean, for example, branched and unbranched alkenyl radicals such as vinyl, propenyl, isopropenyl, 1-butenyl, 2-butenyl, 1-pentenyl, 2-pentenyl, 2-methyl-1-butenyl, 2-methyl-2-butenyl, 3-methyl-1-butenyl, 1-hexenyl, 2-hexenyl, 1-heptenyl, 2-heptenyl, 1-octenyl, 2-octenyl, 1-nonenyl, 2-nonenyl, 1-decenyl, 2-decenyl, 1-undecenyl, 2-undecenyl, 1-dodecenyl and 2-dodecenyl, but also cycloalkenyl radicals having branched or unbranched chains with one or more double bonds, for example cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, 1,3-cyclohexadienyl, 1,4-cyclohexadienyl, cycloheptenyl, cycloheptatrienyl, cyclooctenyl, 1,5-cyclooctadienyl, cyclooctatetraenyl, cyclononenyl or cyclodecenyl.
The organic radicals having up to 12 carbon atoms of this type are preferably C6-C12-aryl radicals or C7-C12-arylalkyl radicals which are unsubstituted or substituted by alkyl radicals. The former radicals include, in particular, phenyl which is unsubstituted or substituted by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, or naphthyl which is unsubstituted or substituted by methyl, and the latter radicals include, in particular, phenylmethyl, 2-phenylethyl, 3-phenylpropyl or 4-phenylbutyl, each of which is unsubstituted or substituted on the benzene ring by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.
Lxe2x80x2, by contrast, is preferably methyl, tert-butyl or phenyl which is unsubstituted or substituted by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.
Possible tridentate chiral ligands L which do not contain P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94 groups, i.e. for which n adopts a value of 0, conform to the formula 
in which the variables have the following meanings:
j is 0, 1 or 2,
k is 0, 1, 2 or 3,
X is oxygen or sulfur,
R4 is methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, halogen, for example chlorine or bromine, nitro, cyano, carboxyl or sulfonyl, where, in the case where k is 2, the two radicals R4 may be identical or different.
R5 to R8 are hydrogen, C6-C12-aryl, for example phenyl, phenyl which is substituted by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, naphthyl or naphthyl which is substituted by methyl, C7-C12-arylalkyl, for example phenylmethyl, 2-phenylethyl, 3-phenylpropyl or 4-phenylbutyl or phenylmethyl, 2-phenylethyl, 3-phenylpropyl or 4-phenylbutyl, each of which is substituted by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, with the proviso that the radicals R5/R6 or R7/R8 in at least one of the radical pairs R5 and R6 and R7 and R8 are different from one another and accordingly at least one of the marked carbon atoms (*) is a center of asymmetry.
Examples of such ligands L are the following (Ph denotes the phenyl radical): 
and the corresponding enantiomeric compounds.
In the case of the compounds of the formula Ib and the preferred embodiments mentioned above, use is preferably made in accordance with the invention of those in which nxe2x80x2 adopts the value 0 for all m Lxe2x80x2(xe2x80x94Y6xe2x80x94M2xe2x80x94Y5xe2x80x94A2xe2x80x94Y4xe2x80x94P2)nxe2x80x2 groups. Use is thus preferably made of compounds of the formula
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)nL]Me(Lxe2x80x2)m 
An analogous situation also applies to the compounds of the formula IIIb and their preferred embodiments mentioned above. Preference is accordingly given here to compounds of the formula
[(P1xe2x80x94Y1xe2x80x94A1xe2x80x94Y2xe2x80x94M1xe2x80x94Y3xe2x80x94)L]Me(Lxe2x80x2)m. 
In accordance with the invention, the compounds of the formulae Ia and Ib and also IIIa and IIIb and their preferred embodiments are used as chiral dopants for liquid-crystalline materials. The term xe2x80x9cliquid-crystalline materialsxe2x80x9d here is not restricted only to materials in which one or more constituents already have liquid-crystalline properties per se (in the temperature range of interest) and are then also present in the materials, but instead is also taken to mean materials in which liquid-crystalline behavior does not manifest itself until the components are mixed or alternatively until the chiral compound(s) Ia, Ib, IIIa and IIIb are admixed (for example lyotropic systems). It should furthermore be noted here that the compounds Ia, Ib, IIIa and IIIb need not necessarily already have liquid-crystalline behavior themselves.
Also claimed are liquid-crystalline materials which comprise at least one compound of the formula Ia or Ib to be used in accordance with the invention or at least one compound IIIa or IIIb (also referred to below as xe2x80x9cdoped LC materialsxe2x80x9d or xe2x80x9cLC materials (according to the invention)xe2x80x9d).
Depending on the specific requirements, these LC materials may contain no, few or many groups which are polymerizable or suitable for polymerization or radicals which carry groups which are polymerizable or suitable for polymerization in the compounds Ia, Ib, IIIa or IIIb and/or the liquid-crystalline base material. Corresponding to the number of reactive radicals of this type in the constituents in the LC materials according to the invention, it is possible to set the desired degree of polymerization, crosslinking and/or condensation after the polymerization or condensation has taken place.
The polymerizable LC materials according to the invention can generally be prepared by mixing polymerizable, liquid-crystalline materials with one or more of the compounds Ia, Ib, IIIa and/or IIIb in a simple manner. Suitable polymerizable, liquid-crystalline compounds are described, for example, in WO 95/22586, 95/24454, 95/24455, 96/04351, 96/24647, 97/00600, 97/34862 and 98/47979 and DE-A 198 35 730 and essentially correspond to the schematic structure Pxe2x80x94Yxe2x80x94Axe2x80x94Yxe2x80x94Mxe2x80x94Yxe2x80x94Axe2x80x94Yxe2x80x94P, in which the variables P, Y, A and M have analogous meanings to the variables P1/P2, Y1 to Y6, A1/A2 and M1/M2 in the formulae Ia, Ib, IIIa and IIIb.
These LC materials according to the invention can serve for the production of optical components, for example LCDs, polarizers or filters.
Furthermore, these LC materials according to the invention can be used for printing or coating substrates. In this case, further additives may also be present. Suitable such additives are those selected from the group consisting of photoinitiators, reactive diluents and diluents, additives selected from the group consisting of antifoams and deaerators, lubricants and flow auxiliaries, thermally curing or radiation-curing auxiliaries, substrate-wetting auxiliaries, wetting and dispersion aids, hydrophobicizing agents, adhesion promoters and auxiliaries for improving the scratch resistance, additives selected from the group consisting of dyes and pigments, and additives selected from the group consisting of light, heat and/or oxidation stabilizers.
The chemical/physical nature of these additives is discussed in detail in the earlier German application 199 05 394.4. Furthermore, this specification describes liquid-crystalline mixtures, as which the LC materials according to the invention, if desired mixed with the abovementioned additives, are also to be mentioned. The doped LC materials claimed in the present application, if desired mixed with said additives, can accordingly, as stated in the earlier German specification 199 05 394.4, be employed as printing and coating compositions for substrates.
Suitable printing or coating substrates, besides paper and board products, for example for carrier bags, newspapers, brochures, gift packaging and packaging materials for utility, semi-luxury and luxury products, are also films, for example for decorative and non-decorative packaging purposes, and textiles of all types and leather.
However, further substrates are also (consumer) electronic products, for example MC, MD, DVD and video recorders, televisions, radios, telephones/cellphones, etc., and computer equipment, products from the leisure, sports, domestic and toy sector, for example bicycles, children""s toys, skis, snowboards and surfboards, inline skates and roller-skating and ice-skating boots, and also domestic appliances. In addition, substrates of this type are also taken to mean, for example, writing utensils and spectacle frames.
However, further substrates are also surfaces to be encountered in the construction sector, such as building walls or even window panes. In the latter case, a functional effect may also be desired in addition to a decorative effect. It is thus possible to produced multilayer coatings on the window material, with the individual layers having different chemical/physical properties. For example, if individual layers of the doped LC materials of opposite twist (through use of the one enantiomer and its optical antipode as dopant in accordance with the present invention) or individual layers of crosslinked, doped LC materials of the same twist direction, but in each case different pitch and thus different reflection properties (through the use of different concentrations of dopant in accordance with the present invention) are applied, certain wavelengths or wavelength ranges of the light spectrum can be reflected specifically. Regarding this aspect of the LC materials according to the invention, especially thermal insulation coatings, reference is also made to DE-A 197 45 647.
The LC materials according to the invention can also be used for the preparation of dispersions and emulsions, preferably based on water. In this respect, reference is made to WO 96/02597 and WO 98/47979, in which the preparation of dispersions and emulsions using liquid-crystalline materials is described.
The LC materials according to the invention can furthermore be used for the production of films. These are taken to mean, in particular, self-supporting layers, as obtained by polymerization of the doped LC materials of corresponding nature. These films may be located on substrates of such a type that it is possible for them to be easily detached and transferred to other substrates to remain there permanently through suitable measures.
Such films can be used, for example, in the area of film coating and in lamination processes.
The LC materials according to the invention are also suitable for the preparation of pigments. In this case, use is made, in particular, of materials which contain a large number of reactive radicals and thus form highly crosslinked polymers. The preparation of such pigments is known and is described in detail in the specification WO 99/11733. In addition, however, pigments of preset shape and size can be prepared using printing techniques with the aid of meshes in whose interspaces the LC materials according to the invention are located. The subsequent polymerization or condensation of the materials is followed here by detachment or removal of the substrate from the mesh. These procedures are described in detail in the specifications WO 96/02597, WO 97/27251, WO 97/27252 and EP 0 931 110.
The polymerizable LC materials are converted into polymers having a frozen liquid-crystalline ordered structure with the aid of their reactive radicals and, depending on their chemical nature, through condensation or free-radical or ionic polymerization processes, which may be initiated by photochemical reactions.
These pigments may be single-layered (homogeneous) or have a multilayered structure. However, the latter pigments can usually only be prepared if use is made of coating processes in which a plurality of layers are generated successively one on top of the other and subsequently subjected to mechanical comminution.
These pigments are used principally in cosmetics, for example for the production of eye-shadow, and in paints for the automobile and leisure sectors.